Role of the dopaminergic system in chronic pain -: a fluorodopa-PET study

Recent data fi um animal experiments suggest an important role for the basal ganglia in the processing and sensorimotor gating of nociceptive information, However, very little is known about their possible participation in human pain. Because of our previous finding of increased excitability of the blink reflex (a brainstem reflex under dopaminergic inhibitory control) in some burning mouth syndrome (BMS) patients, we have studied the dopaminergic function of the striatum putamen and caudatus) of EMS patients with position emission tomography (PET). 6-[F-18]]fluorodopa (FDOPA) PET scans were done on ten EMS patients and 14 healthy control subjects. The presynaptic dopaminergic Function was significantly decreased in the right putamen (20%, P = 0.04) of the EMS patients compared to control subjects. On the left side, the FDOPA uptake was decreased by 17% (P = 0.08). The mean FDOPA uptake was not significantly changed in the caudate nucleus of the patients. The finding of decreased striatal FDOPA uptake in the putamen supports our previous neurophysiological observations indicating decreased dopaminergic inhibition in EMS patients. The present result provides direct evidence of the involvement of the nigrostriatal dopaminergic system in pain for the first time in a clinical pain condition. (C) 2001 International Association For the Study of Pain. Published by Elsevier Science B.V. All rights reserved.